The cupredoxin azurin from Pseudomonas aeruginosa is a promising new therapeutic and diagnostic molecule. Two redox proteins elaborated by P. aeruginosa, the cupredoxin azurin and cytochrome c551 (Cyt c551), both enter J774 cells and show significant cytotoxic activity towards the human cancer cells as compared to normal cells. Zaborina et al., Microbiology 146: 2521-2530 (2000). Azurin can also enter human melanoma UISO-Mel-2 or human breast cancer MCF-7 cells. Yamada et al., PNAS 99:14098-14103 (2002); Punj et al., Oncogene 23:2367-2378 (2004); Yamada et al., Cell. Biol. 7:1418-1431 (2005). In addition, azurin from P. aeruginosa preferentially enters J774 murine reticulum cell sarcoma cells, forms a complex with and stabilizes the tumor suppressor protein p53, enhances the intracellular concentration of p53, and induces apoptosis. Yamada et al., Infection and Immunity, 70:7054-7062 (2002). Azurin also caused a significant increase of apoptosis in human osteosarcoma cells as compared to non-cancerous cells. Ye et al., Ai Zheng 24:298-304 (2003). Rusticyanin from Thiobacillus ferrooxidans can also enter macrophages and induce apoptosis. Yamada et al., Cell Cycle 3:1182-1187 (2004); Yamada et al., Cell. Micro. 7:1418-1431 (2005). Plastocyanin from Phormidium laminosum and pseudoazurin form Achromobacter cycloclastes also are cytotoxic towards macrophages. U.S. Pat. Pub. No. 20060040269, published Feb. 23, 2006. Detailed studies of various domains of the azurin molecule suggested that amino acids 50-77 (p28) (SEQ ID NO: 13) represented a putative protein transduction domain (PTD) critical for internalization and subsequent apoptotic activity. Yamada et al., Cell. Microbial. 7:1418-1431 (2005), although possible routes of cellular entry were not identified
Azurin is now also known to have other pharmacologic activities of therapeutic importance. It is known to inhibit angiogenesis in human umbilical vascular endothelium cells (HUVECs). U.S. patent application Ser. No. 11/488,693, filed Jul. 19, 2006. Azurin from P. aeruginosa is also known for its ability to inhibit the growth of HIV-1 infection in peripheral blood mononuclear cells and to inhibit parasitemia of malaria-infected mammalian red blood cells. Chaudhari et al., Cell Cycle. 5: 1642-1648 (2006). Azurin from P. aeruginosa is also known to interfere with the ephrin signaling system in various mammalian cells and tissues. U.S. patent application Ser. No. 11/436,592, filed May 19, 2006.
Azurin, and in particular, two peptides derived from azurin, an 18-mer and a 28-mer, have therefore been found to be useful therapeutically and diagnostically. However, the efficacy of a therapeutic agent in body of the patient is dependent on several factors. In addition to the activity of the therapeutic drug itself, there are also the pharmacokinetic properties of the therapeutic drug, and how it relates to the various processes that take place after the drug is administered, i.e., absorption, distribution, metabolism and excretion. These pharmacokinetic properties of the drug describe how and to what extent these biological processes influence the efficacy of the administered drug, and these properties include the drug half-life in the blood stream, the hepatic first-pass metabolism of the drug, the volume distribution of the drug, the degree of albumin binding of the drug, etc. Each of these pharmacokinetic properties can have a profound effect on the efficacy of the drug.
The site of absorption of the drug into the bloodstream of the patient depends on the route of administration. For example, orally administered drugs may be absorbed more at one site of the alimentary tract than another site due to the chemical and physical nature of the drug. Absorption by parenteral administration, on the other hand, is not only faster than oral administration, but the blood levels of the drug are far more predictable because much less of the drug is lost, particularly in intravenous administration. The bioavailability is the fraction of the administered drug that reaches the systemic circulation.
The distribution of the drug from the bloodstream into the extracelluar fluid (interstitium) and/or cells of the tissues may be altered by various aspects of the drug. The distribution of the drug in the body may be expressed as the “volume distribution of the drug,” which is a hypothetical volume of liquid into which the drug is disseminated. The structure of the drug may influence the drug distribution in that hydrophobic drugs more readily move across most biological membranes, and thus may be distributed within cells of the tissues. A drug may also be bound to blood proteins and its passage into surrounding tissues thus delayed. For example, when in the blood stream, naproxen is 99% bound to plasma proteins, penicillin G is 60% bound, amoxicillin only 20% bound and minoxidil is unbound. Howard C. Ansel et al., Pharmaceutical Dosage Forms and Delivery Systems 129 (Lippincott, Williams and Wilkins 1999). A bound drug is neither exposed to the body's detoxification processes, nor is it removed from the bloodstream by filtration through the renal glomeruli. The bound drug is referred to as the inactive portion while the unbound portion is considered the active portion. The bound portion of the drug serves as a reservoir of the drug that is then released into the bloodstream in an unbound active form when the level of free drug is no longer sufficient to ensure protein saturation. Therefore, a drug that is bound in the bloodstream will remain in the body for longer periods of time and will require a less frequent dosage.
The metabolism of the drug in the patient will also affect its efficacy. Many drugs undergo biotransformation before being excreted from the body. The biotransformation of a drug may result in a form of the drug that is more water soluble, ore ionized, less capable of binding proteins in the plasma and tissues, less able to penetrate cell membranes, and other aspects that make the drugs less pharmacologically active. The biotransformed drug may therefore be rendered less toxic and more readily excreted. There are four major ways by which drugs are biotransformed: oxidation, reduction, hydrolysis, and conjugation. Oxidation reactions are primarily catalyzed by oxidases bound to the endoplasmic reticulum within the liver cells. Reduction reactions are catalyzed by reductases primarily in the gut and liver. Hydrolytic breakdown is catalyzed by esterases primarily in the liver. Glucuronide conjugation, the most common pathway of biotransformation of a drug, occurs by a combination of the drug with glucuronic acid, forming an ionic form of the drug that is easily eliminated from the body. Christensen et al., J. Pharm. Pharmacol. 37:91-95 (1985). Other biotransformative processes that increase elimination include methylation and acylation.
Excretion of the drug from the body may occur by various routes. The kidney plays the dominant role of eliminating the drug in the urine. However, the drug can also be eliminated from the plasma through the liver. With drugs that are orally administered in particular, the liver may play an important role in determining the plasma half-life of the drug.